全文获取类型
收费全文 | 676篇 |
免费 | 26篇 |
国内免费 | 5篇 |
专业分类
化学 | 550篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 72篇 |
物理学 | 70篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 17篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 32篇 |
2012年 | 45篇 |
2011年 | 70篇 |
2010年 | 29篇 |
2009年 | 23篇 |
2008年 | 45篇 |
2007年 | 54篇 |
2006年 | 44篇 |
2005年 | 37篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有707条查询结果,搜索用时 234 毫秒
701.
Ueki M Galonić DP Vaillancourt FH Garneau-Tsodikova S Yeh E Vosburg DA Schroeder FC Osada H Walsh CT 《Chemistry & biology》2006,13(11):1183-1191
Four adjacent open reading frames, cytC1-C4, were cloned from a cytotrienin-producing strain of a Streptomyces sp. by using primers derived from the conserved region of a gene encoding a nonheme iron halogenase, CmaB, in coronamic acid biosynthesis. CytC1-3 were active after expression in Escherichia coli, and CytC4 was active after expression in Pseudomonas putida. CytC1, a relatively promiscuous adenylation enzyme, installs the aminoacyl moieties on the phosphopantetheinyl arm of the holo carrier protein CytC2. CytC3 is a nonheme iron halogenase that will generate both gamma-chloro- and gamma,gamma-dichloroaminobutyryl-S-CytC2 from aminobutyryl-S-CytC2. CytC4, a thioesterase, hydrolytically releases the dichloroaminobutyrate, a known streptomycete antibiotic. Thus, this short four-protein pathway is likely the biosynthetic source of this amino acid antimetabolite. This four-enzyme system analogously converts the proS-methyl group of valine to the dichloromethyl product regio- and stereospecifically. 相似文献
702.
Gan XM Rapko BM Fox J Binyamin I Pailloux S Duesler EN Paine RT 《Inorganic chemistry》2006,45(9):3741-3745
A multistep synthesis for 2-(2-pyridyl-N-oxide) ethylphosphonic acid 6-H2 is described along with its spectroscopic (IR, NMR) data and a single-crystal X-ray diffraction structure analysis. Combination of the ligand with Nd(OH)3 results in the formation of a complex Nd(6-H)3. Single-crystal X-ray diffraction analysis reveals a three-dimensional crystal network generated by hydrogen-bonded chains along the crystallographic c axis. The hydrogen bonds are formed between phosphonic acid anion (6-H)(-1) protons on one chain and pyridyl N-oxide oxygen atoms in neighboring chains. The asymmetric unit contains 1/3[Nd(6-H)3] and there are two unique Nd(III) atoms, each with point symmetry. As a result, each Nd(III) ion is bound to six (6-H)(-1) ligands and the symmetry about the Nd(III) ion is octahedral with each vertex occupied by a phosphonate oxygen atom. The Nd-O bond lengths are essentially identical: Nd(1)-O(3), 2.336 (1) A; Nd(2)-O(4), 2.340 (1) A. The monoanionic ligand (6-H)(-1), therefore, serves to bridge the unique Nd(III) centers. 相似文献
703.
Flat H-terminated Si(111) substrates modified with alkyl monolayers terminated with hydrophobic and hydrophilic functional groups were prepared using known surface functionalization methods and characterized by FTIR, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The surfaces were then used for the study of non-specific binding of proteins from complex mixtures (using standard mixture of proteins with average molecular weight approximately 6-66 kDa) by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Protein adsorption on these surfaces (following on-probe fractionation of the mixture) was found to be dependent on the nature of surface functional groups, and nature and pH of rinsing solutions used. The results obtained in this work demonstrate that simple silicon-based surface modifications can be effective for direct analysis of complex mixtures by MALDI-MS. Preliminary results obtained using similarly functionalized porous silicon substrates proved that such substrates are (due to their increased surface areas) better performing than flat silicon. 相似文献
704.
Chloé Vovard‐Le Bray Sylvie Dérien Pierre H. Dixneuf 《Angewandte Chemie (International ed. in English)》2009,48(8):1439-1442
Cross‐coupling carbenes : The coupling of a propargylic ester with a diazoalkane in the presence of [RuCl(cod)Cp*] catalyst leads to the formation of functionalized conjugated dienes with high stereoselectivity. The reaction involves the cross‐coupling of a vinylcarbene fragment, arising from a ruthenium‐catalyzed propargylic ester rearrangement, with a diazoalkane carbene.
705.
Romain Breitwieser Paolo Campiglio Cyril Chacon Vincent Repain Ruidy Nemausat Yann Girard Jérôme Lagoute Sylvie Rousset 《Surface science》2012,606(3-4):542-548
The present scanning tunneling microscopy study reports on the growth processes of Co vapor-deposited on a dodecanethiol (DDT) self-assembled monolayer (SAM)/Au(111). We observe strongly modified surface and depth diffusions of Co adatoms depending on the growth temperature. Co deposited at 300 K shows an extremely incomplete regime of condensation on the organic layer. Besides, Co penetrates the DDT monolayer and resides at the DDT/Au(111) interface as 2D clusters. This phenomenon takes place through defects in the SAM which are transient channels. In contrast, Co deposited at 50 K shows a complete condensation and nucleates on defects of the SAM layer as 3D islands sitting most likely on top of the DDTs. These results are of interest in the growing field of organic spintronics where the quality of the organic/ferromagnetic interface is a key issue. 相似文献
706.
707.